Answer:
(x - 4)(x^2 + 7)
Explanation:
x^2 is a factor of the first two terms: x^3 - 4x^2 = x^2(x - 4).
7 is a factor of the last two terms: 7(x - 4).
Note how (x - 4) is a factor of the entire four-term expression given above.
Then: x^3-4x^2+7x-28 = (x - 4)(x^2 + 7)